1. Field of the Invention
The present invention relates to an electroplating apparatus and system, and more particularly to a continuous vertical electroplating apparatus and system.
2. Description of the Related Art
Electroplating is a common process for depositing a thin film of metal or alloy on a substrate such as, for example, a variety of electronic components. In a typical electroplating apparatus or system, the substrate is placed in a suitable electrolyte bath containing ions of a metal to be deposited. The substrate is connected to the negative terminal of a power supply to form a cathode, and a suitable anode is connected to the positive terminal of the power supply. Electrical current flows between the anode and cathode through the electrolyte, and metal is deposited on the substrate by an electrochemical reaction.
In many electronic components it is desirable to deposit the metal film with a uniform thickness across the substrate and with uniformity of composition. However, the electroplating process is relatively complex and various naturally occurring forces may degrade the electroplating process. Most significantly, the electrical current or flux path between the anode and the cathode should be relatively uniform without undesirable spreading or curving to ensure uniform electrodeposition. Furthermore, as metal ions are depleted from the electrolyte, the uniformity of the electrolyte is decreased and must be suitably corrected to avoid degradation of the electroplating process. Additionally, debris and waste particles are generated in the chemical reactions which can degrade the metal film on the substrate upon settling thereon.
Conventional electroplating equipment includes various configurations for addressing these as well as other problems for ensuring relatively uniform electroplating. Suitable circulation of the electrolyte is required for promoting electroplating uniformity, and care is required for properly aligning the cathode and anode to reduce undesirable flux spreading. For example, one type of conventional electroplating apparatus mounts the cathode at the bottom of an electrolyte bathing cell, with the anode being spaced above and parallel to the cathode. Since the substrate is at a common depth in the cell, the electroplating process is less susceptible to vertically occurring variations in the process due to buoyancy or gravity effects or other convection effects occurring during the process. For example, ion depletion in the electrolyte adjacent to the substrate will create local currents which will have a common effect along the horizontal extent of the substrate, but can vary vertically.
Although horizontally positioned cathodic substrates typically result in relatively uniform electrodeposition, the substrates are more prone to the settling thereon of debris particles which degrade the substrate. Also, the various conventional configurations for horizontally electroplating a substrate have varying degrees of complexity which increases the difficulty in mass producing electrodeposition articles. It is desirable to provide not only high uniform thickness and composition in an electrodeposition substrate, but also do so in an apparatus capable of high-volume continuous manufacturing rather than conventional batch systems, and preferably using automated handling equipment.
Thus, it would be desirable to provide a vertical electroplating apparatus and method which allows for a continuous mass-production electroplating process and overcomes the problems associated with conventional electroplating systems. However, a problem that exists with the conventional vertical electroplating apparatus and systems is that the electroplating material is not uniformly distributed on the surface of the substrate to be electroplated, especially in systems attempting to electroplate substrates of varying sizes wherein the length of the anode does not correspond to the length of the substrate. Typically, when the length of the anode does not correspond to the length of the substrate, non-uniform distribution of the plating material occurs with the majority of the coating being concentrated on a particular portion of the substrate. It is inefficient to require the operator of the apparatus to continuously change the size of the anode to match the length of the substrate. Moreover, the anode plates utilized in the conventional electroplating apparatus are often limited to a predetermined size. Therefore, it is substantially impossible to vary an area of the anode depending on the size of a substrate to be electroplated. Thus, an increase in area of the anode relative to the substrate causes a coating thickness on the substrate to be excessively increased at a particular portion and excessively decreased at another portion thereof. This leads to a failure in the formation of a film having a satisfactory uniform thickness which is required on the substrate, thereby resulting in a failure to provide a substrate with satisfactory quality.
Thus, a need exists for a continuous vertical plating apparatus and system which overcomes the problems associated with the prior art (e.g., non-uniform distribution of plating material due to varying substrate sizes, and substrates shifting out of vertical alignment.